A biofilm is a living community of microorganisms including bacteria, fungi and algae. Comprising over 80% of all microbial life on Earth, biofilms stick to surfaces in a layer of EPS (extracellular polymeric substances). This protective shield helps them survive tough conditions.
Biofilms are ubiquitous in nature including in the human body. In regions of human activity biofilms also form on man-made surfaces like pipes, medical devices and swimming pools. Biofilms form on virtually any wet surface.
The first description of biofilm is in the 17th century, when Anton Von Leeuwenhoek, inventor of the microscope, sees these microbial aggregates on scrapings of plaque from his teeth. The term 'biofilm' is credited to Bill Costerton in 1978.
Biofilms originate on early Earth as a protective strategy for prokaryotes, microbial colonists in challenging conditions. Biofilm structures are present in Earth's ancient fossil records dating back c. 3.25 billion years, when Earth is dominated by vast oceans and volcanic tectonics.
Biofilms typically safeguard prokaryotic cells by promoting homeostasis and fostering intricate cellular interactions within the biofilm community. They involve both archaea and bacteria.
Over 70% of all bacterial infections in humans are caused by biofilms. Conversely they can enhance human health and are ecologically important in nutrient cycling and overall ecosystem stability.
The most frequently found bacteria in a biofilm are Pseudomonas aeruginosa, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Streptococcus viridans, Staphylococcus aureus, and Enterococcus faecalis.
What is a Biofilm?
A biofilm is a structured community of microbes. It adheres to a surface and is embedded in a self-produced extracellular matrix. The matrix consists primarily of polysaccharides, proteins, and nucleic acids providing structure for microorganisms within.
Organisms in biofilms include bacteria, fungi, algae, protozoa and viruses. One type of biofilm is Mother of Vinegar, a community formed by acetic acid bacteria. It's used by vinegar artisans to start new batches.
How is Biofilm Formed?
Biofilm formation is a multi-step process that begins with the attachment of free-floating microorganisms to a surface.
Initial Attachment: Microorganisms come into contact with a surface (such as rock, metal, glass, or biological tissues) and attach, often due to physical and chemical interactions.
Irreversible Attachment: Once attached, cells begin to produce an extracellular polymeric substance (EPS) which encases them and assists in binding to the surface and other cells.
Maturation: Over time, the biofilm matures, forming a three-dimensional metropolis, a superstructure of channels for nutrient and waste exchange.
Dispersion: Eventually, for example if food source is depleted or populations grow too large, cells may disperse from the biofilm to colonize new surfaces, perpetuating the cycle.
Various microorganisms can form biofilms, including bacteria like Pseudomonas aeruginosa and Streptococcus mutans, as well as yeast and fungi. Once a biofilm is established, microbes grow and reproduce, forming a structured community.
It's common for multiple bacterial species to coexist in the biofilm, interacting to improve their ability to survive. Mature biofilms contain over 100 different microbial species. They enhance nutrient exchange. Communication among them drives processes unseen by humans.
Slime layers are not usually biofilms as they don't contribute to structure. Due to its loose and flowing nature, a slime layer does not enforce the cell's rigidity. Although biofilms may contain bacteria that produce a slime layer, this is usually not their primary component.
Distinct microenvironments arise, allowing various microbial species to interact. Influencing factors include nutrient availability, flow conditions, and the physical properties of the surface.
Biofilms provide numerous advantages to the microorganisms:
Protection from Environmental Stressors: The EPS matrix shields the microorganisms from harsh conditions, including UV radiation, desiccation, and biocides.
Nutrient Access: Biofilms can create micro-environments that enhance nutrient availability.
Increased Resistance: Biofilms exhibit increased resistance to antibiotics and disinfectants, making infections harder to treat.
Enhanced Communication: Microorganisms in biofilms communicate through chemical signaling, coordinating their behaviors in a process known as quorum sensing.
Biofilms serve several essential functions for the microorganisms that create them. They offer protection from environmental stresses like dehydration, predators, and antimicrobial substances. The protective matrix allows microorganisms to thrive even in hostile environments.
Biofilms enable nutrient sharing and communication among microbial species, or quorum sensing. For instance, when biofilm bacteria sense their population is sufficient, they collectively alter behavior, such as making a coordinated attack on a host during infection.
Biofilms are found in diverse environments across the globe:
Aquatic Systems: Streams, rivers, and lakes often host biofilms on surfaces like rocks and sediments.
Soil: Biofilms contribute to soil health by participating in nutrient cycling.
Industrial Settings: Biofilms can form on pipes and machinery, leading to biofouling, which can cause significant economic loss.
Natural Ecosystems: They play vital roles in bio-geochemical cycles, supporting diverse food webs. They provide essential nutrients to organisms such as fish and invertebrates.
On land, biofilms increase soil health by improving moisture and nutrient retention. Biofilms enhance soil structure and help in water infiltration, reducing soil erosion. The bacteria break down organic materials, releasing important nutrients back into the ecosystem.
Biofilms manifest in different forms depending on the environment and the organisms involved. Some categorization includes:
Single-species Biofilm: Composed of a single type of microorganism.
Multi-species Biofilm: Contains multiple species that often engage in cooperative interactions.
Structured Biofilm: Exhibits complex architecture with distinct layers or zones.
Flat Biofilm: Uniform, thin layers that cover surfaces.
Microbial Mats: Thick, layered biofilms found in extreme environments such as hot springs or salt marshes.
Biofilms can be also be categorized based on their composition, structure, and environmental context. The primary types include:
Environmental Biofilms: These are natural biofilms found in water bodies, soils, and sediments, contributing significantly to ecosystem health.
Medical Biofilms: These biofilms form on medical devices such as catheters and implants. They can cause chronic infections, posing major challenges in healthcare due to their resistance to antibiotics.
Industrial Biofilms: In industrial settings, biofilms can lead to issues like pipeline corrosion, which accounts for approximately 20% of maintenance costs. They can also be beneficial in bioremediation and wastewater treatment.
Extreme Environment Biofilms: Some biofilms thrive in harsh conditions, such as high temperatures or salinity.
Biofilms in the Human Body
Biofilms are present in various parts of the human body and important to health, creating and fighting disease. Common examples include:
Dental Plaque: This familiar biofilm forms on teeth, containing bacteria who cause cavities and gum disease.
Medical Devices: Biofilms can develop on catheters, prosthetics, and other medical devices, complicating treatment and leading to chronic infections.
Intestinal Microbiome: The intestines harbor biofilms active in digestion and immune response.
Diseases such as sinusitis, cystic fibrosis, and certain types of endocarditis are linked to biofilm-forming bacteria. On a positive note, biofilms can be beneficial, maintaining a balanced microbiota, supporting immune functions, and promoting digestive health.
Facts About Biofilm
Pervasiveness: Biofilms can be found almost everywhere—nearly all surfaces in contact with water can harbor biofilms.
Antibiotic Resistance: Bacteria in biofilms are about1000x more resistant to antibiotics than their free-floating counterparts.
Ecological Role: Biofilms are crucial to nutrient cycling in natural ecosystems; they help break down organic materials.
Bioremediation: Certain biofilms can be harnessed to degrade pollutants in contaminated environments, making them valuable in environmental cleanup efforts. Scientists study microorganisms’ natural abilities to clean pollutants
Research: Scientists continue to study biofilms to better understand their complex interactions and devise strategies to manage biofilm-related issues in health and industry.
Biodiversity: A single biofilm can house hundreds of different microbial species, reflecting the complexity of life forms.
Industrial Impact: Biofilm formation accounts for billions in financial losses yearly due to corrosion and biofouling in industries.
Biofilm Disruption Strategies: New biotechnological methods, such as enzyme treatments, are researched to disrupt biofilm formation, improving treatment outcomes for infections.
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